Medical malpractice is a significant problem facing the health care delivery system in the United States. Some studies suggest that a minority of physicians, "bad apples", generate an unusually large number of claims, while other studies have failed to corroborate this finding. Therefore we propose to conduct a retrospective cohort study to address this question more fully. The specific aims of this proposal are: 1) To ascertain whether a population of "bad apple" physicians exist by determining a) if there is a population of physicians who have a "significantly" worse malpractice experience and b) if this experience is consistent over time; 2) To ascertain if there are "bad apple" hospitals in which a) the medical staff has a significantly worse malpractice experience b) the frequency of malpractice incidents is greater at one hospital versus another and 3) To determine if there is an association between malpractice award rate and the Health Care Financing Administration (HCFA) mortality data. The study population will include New Jersey physicians insured by the Medical Inter-Insurance Exchange (MIEX) and the Princeton Insurance Company (PIC). These two companies insure approximately 94% of currently active physicians in New Jersey . MIEX and PIC maintain a computerized database of the claims experience of all insured physicians. Data on physicians who have been insured by both companies can be linked by physician license number. For the physician analyses the primary physician will be identified and three outcomes will be used number of claims, number of awards, and average award payment. All analyses will adjust for time at risk and specialty. We will utilize linear regression analysis to determine if experience is consistent over time. For the hospital analyses we will describe the malpractice experience of the medical staff as well as the frequency of awards that arise from incidents that actually occur in each hospital. We will adjust for the distribution of physician specialists in a hospital size. We will then assess whether these results are consistent over time and whether there is a relationship between malpractice experience and Health Care Financing Administration (HCFA) hospital mortality rates. The generation and resolution of malpractice claims is a complex process and therefore results from the proposed study must be interpreted cautiously. However, we believe the findings from this study will prove both interesting and useful. Current malpractice policy is largely based on the assumption that bad apple physicians exist. Therefore, this study will have a significant implications if this assumption is not supported. Alternatively, identification of 'bad apple' physicians and/or hospitals will provide an appropriate population for additional study of the malpractice process. We intend to use our database to prospectively evaluate "bad apple" physicians and hospitals identified in this study.